In this work, the impact of ErF₃ submicroparticles on the microstructure and mechanical properties of the A359 alloy was studied. ErF₃ particles provided a homogeneous structure in castings produced via the casting method. The modifying effect of ErF₃ particles on the structure of Al–Si alloys is realized through the mechanism of restraining the crystallization front and is achieved through the reduction in the formation of clusters of iron phases and eutectic lamellar silicon. It was found that the addition of 1 wt% ErF₃ to the A359 alloy leads to a decrease in the average grain size by 21% and an increase in the yield strength by 14%, in tensile strength by 16%, in the microhardness of Al₁₅(FeMn)₃Si₂ phase by 34% and in the Al₁₅(FeMnCr)₃Si₂ phase by 7%. The heat treatment of the A359 alloy with ErF₃ particles increased the yield strength by 36% and the tensile strength by 34%. The absence of an effect of ErF₃ particles on the hardness values of the A359 alloy, as well as on the fracture process of the A359 alloy, was observed. The negative influence of ErF₃ particle agglomerates and clusters on the strength characteristics of the investigated alloys was observed. Approaches for further exploring the potential of ErF₃ particles as a strengthening phase in cast aluminum alloys of the Al–Si system were proposed.

Current production requires light and high-strength materials to increase reliability and decrease weight and fuel consumption of means of transportation. The search is being conducted to harden aluminum alloys, showing multiple less density as compared to steel and iron. There are known approaches of dispersion strengthening of aluminum alloys with refractory particles, ensuring an increase in both strength and ductility. It is promising to use erbium fluoride, ensuring an increased density of dislocations in the alloy, and optimizing a process of producing high-strength aluminum alloys. The authors conducted research on the influence of ErF3 sub-microparticles on the microstructure and mechanical properties of АК9 alloy. The authors studied Al – ErF3 alloy combination as required for introducing particles in the molten metal, and combinations of composition – structure – properties of produced alloys in cast and heat-treated conditions. A modifying effect of ErF3 particles on the structure of silumins was determined as taken place according to a crystallization front holding mechanism and grain structure refinement, a decreased formation of clusters of ferrous phases and eutectic plate-like silicon. It has been established that 1% wt. of ErF3 added into АК9 alloy at the casting stage entailed higher homogeneity of the microstructure and refinement of an average grain size of α-Al by 21%. The effect of ErF3 on a deformation behavior of АК9 alloy varies depending on the structural state of the alloy. Adding 1% of ErF3 into АК9 alloy contributes to increase yield strength by 14 and 36%, tensile strength – by 16 and 34% and maximum strains – by 40 and 72% at the stages of casting and heat treatment, respectively. An increase in strength properties of the alloy is stated to be combined with a negative influence of agglomerates of particles and their clusters. The presented research results demonstrate prospects of adding ErF3 particles into aluminum alloys. The paper describes proposed measures aimed at improving a process of manufacturing alloys for improved strengthening effect of particles.Research was funded by the Ministry of Education and Science of the Russian Federation as part of state order No. FSWM-2020-0028.Studies by scanning electron and optical microscopy methods and measurements of hardness and tensile strength properties of the produced alloys were carried out using equipment of the Tomsk Regional Common Use Center of National Research Tomsk State University supported by grant of the Ministry of Education and Science of the Russian Federation No. 075-15-2021-693 (No. 13.TsKP.21.0012).